THE BURNED OVER DISTRICT

But the Trump Doctrine or whatever you may wish to tag his inchoate foreign policy seems to be largely an improvised product. While he did promise all things to all people in his campaign, as the "leader" of a world power, he is expected to follow a reasonably predictable policy.

To the extent that a Trump Doctrine is emerging, it seems to be this: don’t get roped in by doctrine.

In a week in which he hosted foreign heads of state and launched a cruise missile strike against Syria’s government, Mr. Trump dispensed with his own dogma and forced other world leaders to re-examine their assumptions about how the United States will lead in this new era. He demonstrated a highly improvisational and situational approach that could inject a risky unpredictability into relations with potential antagonists, but he also opened the door to a more traditional American engagement with the world that eases allies’ fears.

As a private citizen and candidate, Mr. Trump spent years arguing that Syria’s civil war was not America’s problem, that Russia should be a friend, and that China was an “enemy” whose leaders should not be invited to dinner. As president, Mr. Trump, in the space of just days, involved America more directly in the Syrian morass than ever before, opened a new acrimonious rift with Russia, and invited China’s leader for a largely convivial, let’s-get-along dinner at his Florida estate.

In the process, Mr. Trump upended domestic politics as well. He rejected the nationalist wing of his own White House, led by Stephen K. Bannon, his chief strategist, who opposes entanglement in Middle East conflicts beyond fighting terrorism and favors punitive trade measures against Beijing. And Mr. Trump, by launching the strike on Russia’s ally Syria, undercut critics who have portrayed him as a Manchurian candidate doing the bidding of President Vladimir V. Putin after the Kremlin intervened in last year’s election on his behalf.

Given his unpredictability, none of this means that Mr. Trump has pivoted permanently in any of these areas. The White House has prepared an executive order that the president may sign in the coming days targeting countries like China that dump steel in the American market. And Mr. Trump is sending Secretary of State Rex W. Tillerson on Tuesday to Moscow, where he will have the additional task of trying to smooth over the rancor of recent days, in addition to exploring whether Russia could be a real partner in battling the Islamic State in Syria.

“I like to think of myself as a very flexible person,” he told reporters. “I don’t have to have one specific way.”

That may be fine when you are negotiating a business deal but in world politics, if you stand for nothing you are a threat to everyone.